Can MCI® Fight Microbial Induced Corrosion in Concrete?

Can MCI Fight Microbial Induced Corrosion in Concrete

 

Three of the main causes of corrosion in reinforced concrete are chlorides, carbonation, and sulfates. While Migrating Corrosion Inhibitors have been known to protect against the first two, more research needs to be done on the power of MCI® against sulfates. However, two recent research projects are already suggesting exciting possibilities for the use of MCI® in sulfate rich environments.

The Sulfate Corrosion Problem

Some environments are more corrosive due to a naturally higher level of sulfates. For example, there is typically a higher sulfate content in the ocean than on the land, meaning offshore and marine reinforced concrete structures face the twofold threat of high chlorides and high sulfates. Certain types of soil also have higher sulfates. However, one of the most common culprits for sulfate corrosion is the microbial induced corrosion (MIC) common in wastewater environments. In fact, a wastewater culvert is a perfect breeding ground for sulfate reducing bacteria (SRB) and sulfate oxidizing bacteria (SOB). The result of their sulfate reducing and oxidizing cycles is a high concentration of sulfate that directly eats away at the concrete surface, ultimately leaving rebar exposed to further corrosion and deterioration. Such environments desperately need corrosion inhibitors that will (1) work in the presence of sulfates and (2) ideally protect against sulfate attack on the concrete itself.

MCI® in Research Studies

An independent study published in 2018 by several researchers from the King Fahd University of Petroleum & Minerals in Saudi Arabia helps answer the first concern. The study looked at five concrete corrosion inhibitors, including one “based on amine carboxylate” (as are most MCI® admixtures). The inhibitors were tested in a chloride rich environment with sulfate added at 500 and 2000 ppm.

Almost all inhibitors tested showed only a marginal impact on corrosion inhibiting effectiveness when increasing exposure from 1000 ppm chloride concentration and zero sulfate to 1000 ppm chloride and 2000 ppm sulfate concentration. While amine carboxylate inhibitor efficiency dropped from 85% to 70% with the addition of sulfates at 2000 ppm, it stayed at a significantly high level to warrant use in high chloride-sulfate environments.

Even though calcium nitrite (CNI) inhibitors were tested at a much higher dose (25 times more) than the amine carboxylate inhibitor, they only offered a marginal increase in efficiency levels. In addition, Cortec’s MCI® amine carboxylate admixtures typically offer many advantages over CNI, such as biobased content (e.g., MCI®-2005 is a USDA Certified Biobased Product), certification to meet NSF Standard 61 for drinking water system components, protection against carbonation corrosion, and no acceleration of set time.

Although further research must be done, another whitepaper forthcoming in 2023 also suggests exciting possibilities for the use of MCI® in high-sulfate environments like those with MIC problems. In particular, the chemistries used in MCI®-2005 and MCI®-2018 demonstrated a degree of protection against the deterioration of the concrete itself, not simply protection against rebar corrosion in the presence of sulfates.

Where Do We Go from Here?

These discoveries warrant further investigation and experimentation. In the meantime, specifying engineers working with wastewater and other high sulfate environments should begin to seriously consider the possible benefits of MCI®-2005 admixture and MCI®-2018 two-in-one water repellent / SACI (surface applied corrosion inhibitor) when designing structures and components to withstand these highly corrosive environments. The addition of MCI® to tanks, culverts, and many other structures in the field may lead to further important discoveries in the quest to extend service life in the presence of high sulfates. Contact Cortec® for additional data and consultation: https://www.cortecmci.com/contact-us/

Keywords: microbial induced corrosion, MIC in concrete, extend service life, wastewater corrosion, sulfate corrosion, concrete corrosion, sulfate attack, Cortec, MCI research, rebar corrosion

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NEWS ALERT: MCI® Resilience in Countering Construction Material Shortages

The last two years have been a supply chain roller coaster. In the concrete sector, this surfaced in numerous reports of ready-mixers facing shortages of calcium nitrite or other materials used to enhance concrete durability. The story has been different with MCI® admixtures, which continue to offer a sound and steady solution for corrosion protection and extended service life.

Calcium Nitrite Alternative
MCI® admixtures are much more than mere calcium nitrite inhibitor (CNI) alternatives. For instance, MCI®-2005 is typically easier to work with than CNI because it does not accelerate set time. It uses a fixed dosage rate and goes beyond inhibiting chloride corrosion to also protect against carbonation induced corrosion. Even better, MCI®-2005 is a USDA Certified Biobased Product and is certified to meet ANSI/NSF Standard 61 for drinking water system components.

Galvanized/Epoxy Coated Rebar Alternative
Contractors have also seen shortages of galvanized and epoxy coated rebar. Although a completely different approach to corrosion than specialty rebars, using MCI® admixtures can be a great alternative because they typically offer cost savings in addition to meeting corrosion protection and service life requirements. They also preclude corrosion concerns that arise when the protective layer on galvanized or epoxy coated rebar is chipped.

Pozzolan Alternative
Another construction material in shortage has been pozzolans such as fly ash. While one goal of pozzolans is to help meet strength requirements, the other is to meet durability criteria including protection against corrosive attack. Ready-mix suppliers can adjust various parts of the mix design (e.g., water-cement ratio) to help make up for the first concern, while MCI® admixtures can be used for the latter durability concern by inhibiting corrosion.

A Reliable Supply for Ready-Mixers
Amid the uncertainty of today’s market, MCI® admixtures have remained a strong source of corrosion protection for ready mixers and a sound alternative to other materials commonly used to extend concrete service life. Whether you find yourself facing a material shortage or simply looking for a practical/economical corrosion solution for your concrete structure, contact Cortec® Corporation to learn more about specifying MCI® as a corrosion inhibiting admixture: https://www.cortecmci.com/contact-us/

Keywords: calcium nitrite shortage, supply chain shortages, MCI admixtures, calcium nitrite alternative, epoxy coated rebar alternative, construction material shortages, corrosion protection, MCI, Cortec, extend service life

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Top MCI® Products for Historical Restoration

MCI Mini Grenades

 

Two priorities exist when restoring historical structures that have deteriorated from corrosion: (1) Mitigate corrosion to extend service life and minimize future repairs. (2) Do so without changing the appearance of the structure. This is especially difficult with historical concrete structures, as the addition of new materials could alter the color or texture of the concrete. Fortunately, Cortec® MCI® products have proven to be excellent resources for both maintaining and repairing heritage structures.

Rebar and Concrete Surface Prep

Rebar rust is typically the leading cause of concrete deterioration, and good surface prep is therefore integral to a successful repair. Traditionally this involves labor-intensive sandblasting and cleaning of the rusted rebar to white metal. CorrVerter® MCI® Rust Primer offers a convenient alternative to treat and passivate rusted rebars. A single component, fast drying water based primer, CorrVerter® MCI® can be applied to layers of tight rust, converting it into a hydrophobic passive layer. This method reduces labor and makes re-rusting less likely in the near future. Ash Hasania, Technical Sales & Product Manager for Cortec® MCI®, explained the consequences of overlooking this convenient surface prep method: “You can basically sandblast and not choose any corrosion inhibitor on the steel, but rust is going to come back fairly quickly, and [repair workers] will have to open it up again and clean it and . . . do the same cycle.”

Another important aspect of surface prep is making sure the concrete is clean. For example, concrete contaminated with oils or greases can be cleaned with MCI®-2061 or MCI®-2062. These cleaners contain microorganisms for extended cleaning power. Left overnight, the microorganisms degrade and digest greasy substances within the concrete. They also continue to provide residual cleaning even after the surface has been rinsed off.

Adding Migrating Corrosion Inhibitors to Repair Mortars

One of the most difficult parts of a historical concrete repair can be matching new repair mortars or concrete mixes to the old surface where patching is needed. Sometimes this requires highly specialized historical or decorative concrete mixes. MCI® Mini Grenades can be added directly to these specialty mixes to introduce Migrating Corrosion Inhibitors to the repair. These concrete corrosion inhibitors have been successfully used in historical preservation jobs to extend service life without changing the color or look of the final repairs. They may also discourage the progression of the ring anode effect in areas adjacent to the repair by migrating and evening out the corrosion potential between existing concrete and repaired areas.

Surface Applied Corrosion Inhibitors in Historical Restoration

Surface Applied Corrosion Inhibitors (SACIs) are another important tool in historical restoration and preservation. SACIs can be applied at any stage of a structure’s lifecycle, extending time to subsequent repairs. MCI®-2018 is an excellent option for preventative maintenance because it contains Migrating Corrosion Inhibitors with a 100% silane water repellent to slow the ingress of moisture and chlorides. MCI®-2020 is ideal for heritage structures where corrosion problems have already begun. It contains a higher concentration of corrosion inhibitors, minus the water repellent. Both SACIs are clear and do not change the color of the concrete while allowing Migrating Corrosion Inhibitors to penetrate into the concrete, slow the corrosion process, and extend service life.

Past MCI® Heritage Projects

Cortec® MCI® Technology has been used in many historical restoration projects or heritage structures where minimal change in appearance was as critical as corrosion mitigation.

  • Zagreb Cathedral: Steel joints reinforcing the south tower at regular intervals were coated with CorrVerter® MCI® Rust Primer to arrest the corrosion while minimizing cost and intrusiveness of the repair.
  • Pentagon: Corrosion due to carbonation that extended 3.5 inches (9 cm) deep prompted a major repair on the Pentagon lightwell walls. After 200,000 ft² (18,581 m²) of hand patches were made (using specially cut boards to mimic the pattern created by forms during original construction), MCI®-2020 V/0 was applied over 1,000,000 ft² (92,903 m²) of surface area, along with a silane sealer and mineral-based coating to provide a minimum 20-year design life with the hopes of extending service life by 50 years.
  • New York Hall of Science: The cast-in-place concrete façade of this unique structure had a shallow concrete cover, a common characteristic of brutalist architecture (often coinciding with high porosity) that makes such buildings more prone to corrosion. Repair work included application of MCI®-2020 and a water repellent. Probes were embedded during the repair and subsequently confirmed effective corrosion protection.
  • Memorial University, St. John’s, Newfoundland: The entrance of the education building was adorned with a decorative design in brutalist architectural style. Rebar corrosion took place beneath a very shallow concrete cover. CorrVerter® MCI® was used to passivate the rebar. MCI®-2020 was surface applied to protect the decorative entrance from further corrosion and extend the service life of the repair.

MCI® products are an excellent companion to heritage repairs because they mitigate corrosion without affecting structural appearance. Contact Cortec® to consult on which products may be ideal for your historical or heritage restoration project: https://www.cortecmci.com/contact-us/

Keywords: historical concrete restoration, concrete repair, brutalist architecture, Cortec, MCI, Migrating Corrosion Inhibitors, rebar rust, concrete corrosion, rusted rebar in concrete, From Grey to Green

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NEWS ALERT: How to Mitigate Rebar Corrosion in Precast Concrete

Precast concrete is a high-quality building material with countless uses: for bridges, parking ramps, light poles, culverts, prefab houses, tanks, and much more. Since precast concrete is made and cured in a controlled environment, it has a low risk of corrosion vs. cast-in-place concrete. That is . . . until cracking occurs, as can often happen during transportation. Once cracks form, corrosives can enter and additional freeze-thaw cracking can occur, leading to long-term corrosion damage. Fortunately, Cortec® MCI® is an easy way to arrest corrosion and extend service life at any stage in the precast concrete lifespan.

MCI® Admixtures for New Precast Elements
Although many engineers understandably see no need to add corrosion inhibitors to the precast concrete mix, this is the best place to do so to minimize future problems when long service life is desired. Admixtures such as MCI®-2005 NS do not negatively affect the ready-mix. They introduce Migrating Corrosion Inhibitors that form a protective molecular layer on the surface of metal reinforcement, delaying time to corrosion and reducing corrosion rates once started. Precast elements that contain an MCI® admixture are already prepared to fight corrosion if cracking occurs from normal wear and tear in transit.

MCI® SACIs for Existing Precast Elements
While the use of MCI® admixtures is ideal, sometimes it is difficult to convince decision-makers that another product is needed until the problem becomes obvious. Conveniently, MCI® comes in multiple forms that can be applied even after concrete elements are cast. For example, an excellent response to finding cracks on precast bridge segments stored at the construction site is to apply an MCI® SACI (surface applied corrosion inhibitor). MCI®-2020 offers the highest concentration of Migrating Corrosion Inhibitors that penetrate into concrete and eventually make their way to the reinforcing steel. The addition of a water repellent helps seal the MCI® in and corrosives out. Another option is to apply a twoin-one MCI® water repellent such as MCI®-2018. This SACI combines Migrating Corrosion Inhibitors with a 100% silane water repellent that guards against the intrusion of water, chlorides, and carbonation. 

MCI® for Precast Concrete Repair
Sometimes, corrosion has already gone so far that precast concrete elements must be repaired. MCI® Technical Sales and Product Manager, Ash Hasania, found this to be the case when he encountered a client with deteriorating concrete light poles that were more vulnerable to corrosion because of old, poor quality concrete cast in a slender design. MCI®-2023 was used to re-passivate rusted rebars. MCI® Mini Grenades were added to the ready-mix for the new concrete patches. Once the concrete cured, surfaces were treated with MCI®-2020 and MCI®-2018 for additional corrosion protection. Going forward, the customer began adding MCI®– 2005 to the light poles during casting.

Precast and Prevent with MCI®
Precast concrete is everywhere: along the road, under the ground, and sometimes even at home. In spite of the quality advantages of precast concrete vs. cast-in-place concrete, prefab elements still face corrosion risks as a result of cracking and other issues. MCI® offers a simple solution to extend the service life of precast concrete early or late in the process.

Contact Cortec® MCI® to learn more about fortifying your precast concrete structures with Migrating Corrosion Inhibitors: https://www.cortecmci.
com/contact-us/

Keywords: precast concrete lifespan, precast concrete vs cast in place, extend service life of concrete, MCI, Migrating Corrosion Inhibitors, From Grey to Green, Cortec, how precast concrete is made, admixtures, rebar corrosion in concrete

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NEWS ALERT: Four Great Reasons to Attend World of Concrete 2023!

Calling all MCI® reps and distributors!!! It is that time of year again!

With construction season winding down and January fast approaching, it is not too early to start planning your visit to the World of Concrete 2023! Here are + four not-to-miss opportunities for Cortec® MCI® reps and distributors next January 16th-19th in Las Vegas:

1. Take advantage of one-on-one time with your Cortec® MCI® rep (contact your rep to secure a time slot now).
2. Grow your concrete repair network and have fun at the Monday night ICRI kick-off event.
3. Catch up, connect, and be inspired at our MCI® rep meeting (ask about MCI® repair mortar updates and testing).
4. Enjoy our invitation-only fun activity for MCI® reps and distributors!

You are also welcome to simply hang out with the MCI® team at Booth #S10856 during exhibit hours Tuesday through Thursday (January 17th-19th), or explore the grounds to check out the wealth of educational resources and networking opportunities at your fingertips during the only annual international event dedicated to commercial concrete and masonry industries!

Contact your rep today to schedule a one-on-one: https://www.cortecmci.com/contact-us/

Get registered with ICRI promo code A36: https://www.compusystems.com/servlet/ar?evt_uid=130&promocode=A36

World of Concrete 2023
January 17th– 19th, 2023 (Exhibits)
Las Vegas Convention Center
Las Vegas, NV
Booth # S10856
www.worldofconcrete.com

Keywords: WOC2023, World of Concrete, Cortec MCI, reasons to attend WOC, ICRI, From Grey to Green, construction industry, MCI repair mortars, concrete repair

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